﻿using System;

namespace Problem_4_Odd_Number
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            long result = 0;
            for (int i = 1; i <= N; i++)
            {
                long number = long.Parse(Console.ReadLine());
                result ^= number;
            }
            Console.WriteLine(result);
        }
    }
}
